Controller Board Circuit Operation - Motorola HT 1000 series Theory/Troubleshooting Manual

(J701 pin 9) to go low. The multiprocessor detects
this transition using U710, and then sends a com-
mand to the display in order to read the keypad
data.
The secure/data option board, which connects to
connector jack J702, supports two slave SPI
devices, which can each return data to the multipro-
cessor. The connector pins for these devices are
J702 pins 21 and 23, and the interrupt lines (which
performs the same function as the KEY INT line
above) J702 pins 20 and 22. These lines connect to
the SLIC IV (U710) at PK5, PK0, PH4, and PJ4,
respectively.
9. Option Select Lines
The two option select lines OPT SEL 1 and OPT
SEL 2, pins 1 and 5 of the universal connector, are
used to identify the presence of external acces-
sories and also to key up the radio with an external
microphone. Table 1 (previously illustrated in the
closed architecture controller section) shows the
modes indicated by the various combinations of the
signal states. Note that both signals have pullup
resistors on the controller board (R702 and R717),
so that if no external device is connected to these
pins, they will be at a logic-high level and the radio
will be in the normal mode; i.e., internal speaker and
microphone will be used. Note also that RF power
will always be routed to the internal antenna port
unless a side connector is installed that activates
the electro-mechanical switch inside the transceiver
board which redirects power to the external antenna
port. The microprocessor has no knowledge or con-
trol of which port transceiver energy is being
directed. An external PTT (OPT SEL 1 =0, OPT
SEL 2=0) will cause the external mic audio port to
be activated, but the RF could be routed through
either RF port.
10. LED Control
The bicolor LED on the top of the radio is activated
by U710 output ports PK7 and PL7, in conjunction
with the dual NPN transistor IC, U704. When either
output is at logic high, the corresponding output pin
of U704 (pin 6 for the green LED, pin 3 for the red)
should be at approximately 4.3 volts. Note that it is
possible to have both LED outputs on simultaneous-
ly, in which case the LED emits a yellow/ orange
light.
11. Secure Board Interface
The radio can provide secure voice encryption using
an optional secure board (with a number of possible
encryption algorithms) connected to connector jack
J702. A standard Motorola key-variable loader can
be used to transfer key to the secure board. The
keyloader connects the signals DVP WE, KID, and
KEY/FAIL to the radio universal connector pins 7, 9,
and 11, which correspond to controller connector
24
jack, J701 pins 21, 22, and 26. In addition, the key-
variable loader identifies itself by grounding
universal connector pins 10 and 12, which corre-
spond to controller connector jack, J701 pins 23 and
25. When the microprocessor detects these pins at
a logic-low level, it then sets the control line labelled
MUX CNTL for mux U711 to a logic one, which
causes it to select the lines X1, Y1, and Z1. These
are the DVP WE, KEY INSERT DATA, and
KEY/FAIL lines from the secure board connector
jack J702. The keyloader can then be used to trans-
fer keys to the secure board.
B. Controller Board Circuit Operation
The circuits to be considered here are:
• the transmit audio path between the microphone
and the transmit RF section,
• the transmit data path between the microprocessor
and the RF section,
• the receive audio path between the receive RF sec-
tion and the speaker,
• the receive data path between the receive RF sec-
tion and the microprocessor, and
• the alert tone path between the microprocessor and
the speaker.
The transmit and receive audio paths are disabled
in the standby mode and selectively enabled by the
microprocessor when the radio transmits or receives a
signal. Also, there are minor differences in the function-
ing of both paths depending on whether an internal or
external (accessory) microphone/speaker is being used.
The radio constantly monitors the received data path for
control-channel data in trunking operation or sub-audi-
ble data in conventional operation.
1. Transmit Audio Circuits
There are three major circuits in the transmit audio
path. Some require enable lines and some are
active devices that are always operating. When the
operator presses the PTT while in trunked mode,
the radio will request a channel from the control
channel. When it receives a grant it will move to the
specified voice channel and the microprocessor will
enable the path between the microphone and the
RF section. When the operator presses the PTT
while in conventional mode, the radio will first moni-
tor the channel for traffic (smart PTT) and if it is not
busy the microprocessor will enable the path
between the microphone and the RF section.
The microphone used in the radio front cover (inter-
nal mic) and remote microphone (external mic) are
of the FET electric type and, thus, require a dc bias-
ing voltage provided by R703 and R706,
respectively. Note that there are two distinct micro-
phone audio input paths (U701-A7 and U701-B8)
for amplification; logic inside the ASF IC (U701) is
used to select one of the signals.